A variety of electrical connectors are designed for utilization with a flat flexible circuit which may be mounted directly on the connector or connected in circuit with terminal pins on the connector. Generally, flat flexible circuits include a flat flexible dielectric substrate having one or more holes therein for receiving one or more terminal pins. A ductile conductive film or other circuit trace system is deposited on the substrate in an area at least about the hole or holes. The terminal pins are inserted into the holes in the substrate to establish electrical and mechanical connections between the pins and the flat flexible circuit. Normally, each hole is smaller in diameter than a respective pin. Alternatively, the pin may be punched through the flat flexible circuit to establish the electrical and mechanical connection therewith.
In order to assure good electrical and mechanical connections in these types of electronic devices or electrical connectors, solder or other adhesives often are used. For instance, in U.S. Pat. No. 4,970,624, dated Nov. 13, 1990 and assigned to the assignee of the present invention, uni-axial adhesive is deposited on the flat flexible circuit about the hole which is penetrated by the terminal pin. The adhesive includes a non-conductive base incorporating randomly spaced conductive particles. When the terminal pin is forced through the adhesive, a portion of the adhesive is carried with the terminal pin between the pin and the flat flexible circuit. The carried portion of the adhesive is compressed for establishing contact between the conductive particles and, thereby, conductivity between the terminal pin and the flat flexible circuit, leaving the adhesive other than that portion in a non-conductive state. Such adhesives often are called "Z-axis" adhesives. These adhesives were developed to replace soldering techniques which require specific temperature resistant components and substrates. Although such adhesives serve their intended purposes, they are relatively expensive and, for that reason, undesirable in some applications.
Flat flexible circuitry often is used in environments wherein the circuitry must be protected from disruptions or "noise" caused be electromagnetic interference (EMI), radio frequency interference (RFI), electrostatic discharges (ESD) and/or electromagnetic pulses (EMP). Such applications may range from use in high frequency pulse circuits, such as computers and vehicles, wherein signals are generated which will cause radio frequency interference and electromagnetic interference to nearby radio and other electronic devices, to other applications wherein equipment must be protected against power surges owing to electrostatic discharges and electromagnetic pulses as well. A high voltage generated by electrostatic discharges and electromagnetic pulses can damage voltage sensitive integrated circuits and the like.
In environments as described above, including automotive applications, it is desirable to provide the connector assembly with a filtering capability, such as to suppress EMI and RFI, and transient suppression of EMP and ESD interference or other undesirable signals which may transit circuits terminated to the connectors. Employing filter components in a connector assembly creates problems in manufacture and assembly because of the undue complexity of the connectors, particularly in substantially increasing the assembly costs of the connectors. In the extremely high volume environment of automotive applications, cost considerations can be extremely important. In high density, high circuit count connectors, such as the main connector assembly of an automobile, still additional considerations must be addressed in mounting the connector assembly to a printed circuit board and still employ all of the necessary filter components. A solution to this myriad of problems is shown in co-pending application Ser. No. 07/962,763, filed Oct. 19, 1992, which is assigned to the assignee of the present invention and which is incorporated herein by reference.
In particular, in that co-pending application, flat flexible circuitry is employed and is mounted directly on to the connector housing, such as a rear face of the housing. The flat flexible circuitry is a flexible capacitor filter circuit which includes a plurality of chip capacitors operatively associated with tail portions of the terminals of the connector projecting from the rear face of the housing and passing through the flexible capacitor filter circuit.
In applications as described above, the connector housing may be fabricated of die cast metallic material, such as of magnesium, aluminum and the like. The ductile film on the flat flexible circuit is fabricated of a different metallic material, such as copper or the like and, in fact, may be plated with still a different metallic material such as a tin/lead alloy. The conductive film on the flat flexible circuit acts as a ground plane against the rear face of the connector housing. The housing has a plurality of pins which project through holes in the flat flexible circuit. Using a "Z-axis" adhesive between the housing pins and the flat flexible circuit not only is expensive, as described above, but the conductive interface between the different metal components is limited to the areas of pressure.
The present invention is directed to solving the sizable myriad of problems identified above by utilizing a particular interfacing system between a conductive pin and a flat flexible circuit wherein different interfacing metal components are encountered, with a desire to ensure a reliable electrical/conductive interface over the life of the connector.